An even stronger magnitude 7.1 earthquake rocked southern California Friday evening at 8:19 p.m. local time, raising fears that powerful aftershocks were likely to continue. There was significant structural damage to road, water and gas lines in the latest quake.
The epicenter was northeast of Ridgecrest, near the location of the Fourth of July “foreshock” that caused pockets of damage. The area is about 150 miles northeast of Los Angeles in the Mojave Desert.
Seismologists had warned that there was a chance of a stronger earthquake following the first event on Thursday, and that threat — 10 percent — still exists.
Since the precursor earthquake on July 4, more than a thousand aftershocks of magnitude 2.5 or greater have occurred along the branching fault, which is part of the San Andreas system — but not the infamous fault 95 miles to the southwest.
Seismic waves triggered by the magnitude 6.4 earthquake that rattled southern California on Thursday were recorded on a seismograph at Shawnee State Forest in Portsmouth — more than 2,500 miles away.
The Ohio Seismic Network, or OhioSeis, is a cooperative network of Ohio seismic stations operated by the Ohio Department of Natural Resources that continuously records earthquake activity.
Former Hilliard resident, Josh Gelber, 28, moved to Los Angeles four days before the July 4 earthquake. He described “a good 20, 25 seconds of kind of a low rumble.”
He said the Friday evening quake was felt more sharply — like a powerful jolt — than the first earthquake, described by U.S. Geological Survey as an earthquake sequence.
Gelber was an Ohio University student on Aug. 23, 2011, when the building shook, following a magntude 5.8 earthquake centered in southeastern Virginia.
“Earthquakes in the eastern U.S. have a felt area about ten times larger than a comparable earthquake in the western U.S,” said Daniel Blake, a geophysicist with ODNR’s Division of Geological Survey.
“In Ohio, rocks are nearly flat lying, brittle, and cold. These characteristics are favorable for seismic waves to travel longer distances without losing significant energy,” Blake noted. “In contrast, California earthquakes, for example, travel through less consolidated, warmer rocks that are interrupted by mountain ranges and other features that tend to absorb (attenuate) seismic energy.”
The first California quake occurred at 1:33 p.m. local time on Thursday. The earthquake, which occurred 6.6 miles below the surface, was caused by a shallow strike-slip fault, a nearly vertical fracture that results in a horizontal displacement of strata.
Approximately 50,000 people submitted reports that they felt the the main California earthquake on the Fourth of July, including the areas around Los Angeles and Las Vegas, according to the United States Geological Survey.
Blake said that the Ohio Seismic Network is in the process of installing 10 more sites to improve the real-time monitoring capabilities.
“Data are transmitted in real time back to the Ohio Earthquake Information Center at Alum Creek State Park for earthquake analysis.”
The information is shared with the scientific community through the Incorporated Research Institutions for Seismology Data Management Center,” Blake said.
“Additions to the network will increase our understanding of the state’s seismicity and assist in keeping Ohioans safe,” said Blake.